ABSTRACT
We report a 64-year-old male patient without any contributory medical history who visited the eye clinic due to right-sided headache for 1 month and then loss of vision for 3 days. The clinical presentation suggested a cavernous sinus syndrome and acute optic nerve ischaemia in his right eye. The left eye was normal. Orbit and brain magnetic resonance (MR) imaging demonstrated restricted diffusion of the posterior orbital segment of the right optic nerve, suggesting an acute posterior ischaemic optic neuropathy. Three-dimensional time-of-flight MR angiography showed high flow in the right cavernous sinus, indicating a carotid cavernous fistula (CCF). In the arterial phase of digital subtraction angiography (DSA), a fistula in the right cavernous sinus was revealed which was fed by meningeal branches from both the external and internal carotid arteries, confirming an indirect CCF. The origin of the right ophthalmic artery was seen, but its branches were not detected. Right common carotid artery DSA showed a superior ophthalmic vein occlusion and the drainage vein of the CCF ran through the inferior petrosal sinus to the internal jugular vein. The right cavernous sinus was embolised using platinum coils and glue to occlude the feeding vessels from the branches of both the external and internal carotid arteries. Post-embolisation imaging showed complete closure of the fistula.
KEYWORDS: dural carotid cavernous fistula, superior ophthalmic vein occlusion, posterior ischaemic optic neuropathy
Case presentation
A previously healthy 64-year-old male patient presented with vision loss in his right eye (OD) for the last 3 days. He reported right-sided headache for 1 month prior but denied recent trauma. His medical history regarding infective and inflammatory processes was insignificant.
There was no audible bruit, but intermittent pulsatile proptosis was noticed in his right eye. His visual acuity was counting fingers at 1 m OD with a marked relative afferent pupillary defect, right ptosis, and generalised ophthalmoparesis. Corneal and facial sensation was normal bilaterally, and slit-lamp examination showed dilated and tortuous episcleral veins OD (Figure 1). The right anterior segment was clear without any blood reflux in Schlemm’s canal. Funduscopy as well as fluorescein angiography showed no abnormality at the first visit (Figure 2). His left eye (OS) was normal. Intraocular pressures were 17 mmHg OD and 18 mmHg OS. Neither focal neurological deficit nor systemic disorder was detected.
Figure 1.
Right exophthalmos with dilated and tortuous episcleral veins.
Figure 2.
No abnormality found in both the fundus photograph (a) and fluorescein angiogram (b) in the first visit in the right eye, which has counting finger vision.
He did not have Horner’s syndrome nor trigeminal sensory loss. The differential diagnosis therefore was between a right orbital apex syndrome versus an atypical cavernous sinus syndrome and acute optic nerve ischaemia in the right side, potentially from a cerebral vascular abnormality. Hence, orbit and brain magnetic resonance (MR) imaging was performed. This demonstrated restricted diffusion of the posterior orbital segment of the right optic nerve, suggesting an acute posterior ischaemic optic neuropathy (Figure 3a,b). Three dimensional time-of-flight (TOF) MR angiography showed high flow in the right cavernous sinus, (Figure 3c) indicating a carotid cavernous fistula (CCF), but no dilated superior ophthalmic vein was found. Hence, digital subtraction angiography (DSA) was employed to confirm the diagnosis of a CCF. Because he first visited an eye hospital, he was referred to a general hospital with interventional radiology to have his DSA performed. This occurred 2 days later but his vision dropped to no perception of light (NPL) OD on the day of the DSA.
Figure 3.
Restricted diffusion in the right optic nerve on (a) diffusion weighted imaging and (b) apparent diffusion coefficient map consistent with posterior ischaemic optic neuropathy (arrowed). (c) High signal ”dot-like” appearance of the right cavernous sinus on time-of-flight magnetic resonance angiography sequence (arrowed).
The DSA demonstrated a fistula in the right cavernous sinus, which was fed by meningeal branches from both the external carotid artery (ECA) and the internal carotid artery (ICA), confirming an indirect CCF (Figure 4d). The origin of the right ophthalmic artery was seen, but its usual branches were not detected (Figure 4a). In contrast, a normal vascular network of the left side was clearly demonstrated with all branches (Figure 4b). Right common carotid artery DSA showed superior ophthalmic vein occlusion and the drainage vein of CCF ran through the inferior petrosal sinus to the internal jugular vein (Figure 4c).
Figure 4.
(a) Visible root of the right ophthalmic artery without branches seen (arrowed). (b) Normal vascular network on the left side. (c) Right superior ophthalmic vein occlusion (arrowed). (d) Branches of the right external carotid artery feeding the right dural carotid cavernous fistula.
Based on these findings, endovascular fistula embolisation was recommended. The right cavernous sinus was embolised using platinum coils and non-adhesive glue (ethylene vinyl-alcohol copolymer) to occlude the feeding vessels from the small branches of both the ECA and the ICA. Post-embolisation imaging showed complete closure of the fistula. One month after the intervention, his headache had resolved although his vision remained at NPL OD. Temporal pallor was noted in the right optic disc, but there was no significant change in the intraocular pressure, vascular engorgement of the episcleral vessels, proptosis, ptosis, or ophthalmoparesis in the right side.
Discussion
A dural CCF occurs due to pathological communication between meningeal branches of ECA, ICA, or both with the cavernous sinus.1 In dural CCFs, disturbed flow may cause a remodelling process of the venous endothelium and venous arterialisation, leading to superior ophthalmic vein occlusion.2–4 In our case, we hypothesise that the capillary pressure increase could have been the consequence of long-lasting ophthalmic vein occlusion, which reduced flow in the ophthalmic artery branches. This is similar to the mechanism of ischaemic retina in central retinal vein occlusion and could explain the angiographic manifestation of the right ophthalmic artery branches.5 Steal phenomenon in which blood from ophthalmic artery is stolen through the dural CCF might be a mechanism explaining the reduction of blood supply to the posterior orbital segment of optic nerve.6,7 In this case, ophthalmic vein obstruction was overlooked on TOF MR angiography because of the low flow in the dural CCF.
Restricted diffusion can be detected in inflammatory, infiltrative, or ischaemic lesions of the optic nerve; however, the diagnosis of ischaemia was made in our case based on the focal restricting lesion with no other evidence for local or systemic disease.
Recently, Daniel et al. described a case with sudden visual loss owing to central retinal artery occlusion and posterior ischaemic optic neuropathy from a spontaneous direct CCF.8 However, our patient only presented with a low-flow vascular shunt and no retinal process was detected. Therefore, the clinical features of CCF in the case described by Daniel et al. were much more prominent than in ours.
Dural CCF-related ophthalmic vein occlusion and posterior ischaemic optic neuropathy are uncommon. Our patient manifested with an atypical cavernous sinus syndrome and acute vision loss over nearly one week. A potential fistula should be taken into account in any patient with unexplained vision loss and accompanying signs such as proptosis and/or dilated episcleral vasculature. All in all, the time-critical nature of the whole diagnostic and interventional process must be seriously considered to preserve as much visual function as possible.
Funding Statement
The authors reported that there is no funding associated with the work featured in this article.
Declaration of interest statement
No potential conflict of interest was reported by the authors.
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